The Nervous System The Nervous System Introducion Introducion

Overview• Functions• Organization• Protection

Functions• Monitor activities of body parts -

sensory neurons

• Communicate between body parts - associative neurons

• Command necessary action - motor neurons

Functions• The nervous system is a fast acting

control center; it gathers, integrates, stores and recalls information, and acts upon that information to ensure survival.

Organization: Divisions of the Nervous System

• Central Nervous System (CNS)-brain-spinal cord

Organization: Divisions of the Nervous System

• Peripheral Nervous System (PNS)-cranial nerves-spinal nerves

• Has two subdivisions: somatic & autonomic

Organization: Divisions of the Nervous System - PNS• Somatic nervous system - voluntary,

contains sensory & motor neurons; stimulates skeletal muscle

Organization: Divisions of the Nervous System - PNS• Autonomic nervous system -

involuntary; controls action of cardiac and smooth muscle as well as glands

• Two subdivisions: sympathetic & parasympathetic

Organization: Divisions of the Nervous System - PNS

• Sympathetic system = “fight or flight” response activated during times of stress = increased heart rate, blood pressure, etc.

• Also referred to as the “E” system for exercise, excitement, emergency, & embarrassment

Organization: Divisions of the Nervous System - PNS

• Parasympathetic system = “housekeeping” in effect most of the time; maintains homeostasis

• Also referred to as the “D” system for digestion, defecation, and diuresis (urination)

Protection of the Nervous System

• Bones - skull protects brain; vertebrae protect spinal cord

• Cerebrospinal Fluid (CSF) - watery fluid formed from plasma that circulates through the central nervous system and function as a shock absorber

Protection of the Nervous System

• Blood-Brain Barrier - made of the least permeable capillaries in the body, keeps neurons separated from many substances in the body to help prevent uncontrolled neural activity

Protection of the Nervous System

• Blood-Brain Barrier - keeps out metabolic wastes such as urea, toxins, proteins, and most drugs -also keeps out nonessential amino

acids and potassium -does allow essential amino acid, water

and glucose

Protection of the Nervous System

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Protection of the Nervous System

• Meninges - 3 layered connective tissue membranes that cover & protect the brain and spinal cord

• Layers in order of outermost to innermost: Dura mater, Arachnoid membrane, and Pia mater

Meninges• Dura mater = “tough mother”, leathery

and made up of two layers that forms the outer covering of the brain as well as the periosteum of the skull

Meninges• Arachnoid membrane - middle layer with threadlike extensions giving a cobweb like appearance. Has subarachnoid filled with CSF

Meninges• Pia mater = “gentle mother”, innermost layer, delicate and highly vascularized (rich blood supply)

The End!